Keratomycosis is an infection of the cornea induced by fungi (mold), and is also called mycotic keratitis. Keratomycosis is known to occur from an injury by a plant or the like, continuous wear of soft contact lenses, long-term use of steroid eye drops, or the like. Keratomycosis is often difficult to diagnose and, in addition, unless appropriately treated at an early stage, becomes intractable and leaves severe corneal scars, resulting in decreased vision.
A generally used ethical drug for keratomycosis is natamycin eye drops. Natamycin eye drops usually need to be administered one drop at a time and multiple times a day. Natamycin eye drops are also known to have low corneal permeability of the drug and provide insufficient therapeutic effect (Non-Patent Literature 1, Non-Patent Literature 2). On the other hand, rapamycin (also called “sirolimus”) is a metabolic product of the actinomycete Streptomyces hygroscopicus isolated from soil of Easter Island, and was found in the 1970s as a macrolide antibiotic. Rapamycin was then found to have immunosuppressive activity, was approved in the United States and Europe as having the efficacy “prevention of organ rejection in kidney transplant patients”, and has been marketed under the trade name “Rapamune (registered trademark)”.
Patent Literature 1 discloses rapamycin's effect of decreasing vascular hyperpermeability.
Patent Literature 2 discloses a composition and the like for treating age-related macular degeneration (also called “AMD”).